What does this research mean for the field?

Compost tea application at a dose of 680 mL m−2 increases nitrogen use efficiency and lettuce yield under suboptimal fertilization conditions. Novelty: ClaimNovelty.NOVEL_FINDING. Consensus alignment: ConsensusAlignment.SUPPORTS_CONSENSUS.

What question did this study set out to answer?

The research aims to evaluate the effectiveness of compost tea in improving nitrogen use efficiency in lettuce cultivation under varying fertilization conditions.

March 12, 2026Open Access

Compost tea as a tool for sustainable nitrogen management and microbial stimulation in lettuce cultivation

Key Points

The research aims to evaluate the effectiveness of compost tea in improving nitrogen use efficiency in lettuce cultivation under varying fertilization conditions.
Examined nitrogen use efficiency in lettuce treated with different doses of compost tea (0, 170, 340, 680 mL m−2)
Conducted soil and microbial analyses to assess enzymatic activity and mineral content
Measured biometric parameters related to fresh biomass production under no fertilization, suboptimal, and optimal conditions.
Compost tea application improved yield by 15.7% and nitrogen uptake by 14.7% under suboptimal conditions.
The amoAOB gene associated with ammonia oxidation increased with higher compost tea doses.
A dose of 680 mL m−2 of compost tea showed a decrease in nitrogen uptake and gene abundance under optimal conditions.

Abstract

• The positive effects of compost tea are influenced by the dose and level of fertilization. • Under suboptimal conditions, application of compost tea improves lettuce production. • The use of compost tea is a valuable tool for increasing nitrogen system efficiency. • Nitrogen-cycle genes show pathway-specific responses to fertilization and compost tea. In a context where agriculture is called to combine productivity, resource efficiency and resilience to climate change, reducing the use of synthetic fertilizers is imperative. This study evaluated Nitrogen Use Efficiency (NUE) in a lettuce ( Lactuca sativa L.) crop treated with four increasing doses (0, 170, 340, and 680 mL m −2 ) of compost tea (CT) under no fertilization (NoFert), sub-optimal (Half), and optimal (Full) conditions. Considering the complex interactions between soil and plants, enzymatic and microbiological analyses of the soil were conducted, the mineral content in the soil and leaf tissues were determined and the biometric parameters associated with fresh biomass production were measured. The results show that only plants grown under suboptimal fertilization conditions got a boost from CT. Specifically, the highest dose led to an increase in yield (+15.7 %) and N uptake (+14.7 %) compared to the control without CT (Half x 0). This effect was related to a higher amount of the amoAOB gene, which is involved in ammonia oxidation. On the other hand, the apr and ureC genes showed an increase at the 340 but a decrease at 680 mL m −2 of CT. This suggests dose-dependent microbial responses. Under optimal fertilization conditions, the application of the highest dose of CT reduced the abundance of all genes analyzed and N uptake compared to the control (Full x 0). From an agronomic point of view, the application of CT at a dose of 680 mL m −2 is promising for reducing the use of synthetic fertilizers, reducing the production gap between optimal and suboptimal fertilization, while increasing the NUE of lettuce.

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